Impervious surfaces are areas that impede the infiltration of water into the soil (rooftops, driveways, parking lots, roads, severely compacted soil, etc). When it rains, water flows over impervious surfaces and is directed to a waterway or into a stormwater drain/inlet. As the water travels, it picks up debris, dirt, pesticides, excess nutrients from fertilizers, litter, pet waste, fluids from leaking cars and other pollutants. Stormwater drains are connected to a series of underground pipes that lead to streams or rivers. These systems are not designed to capture debris or treat the water as in a sanitary system that leads to a wastewater treatment plant. Thus once the runoff enters the stormwater system, it travels unfiltered and untreated directly to local waterways. This pollutant load is harmful to the aquatic environment and degrades the stream’s water quality. In addition, the sudden surge and velocity of runoff during a storm event causes stream erosion, floodplain degradation and possible flooding.
NPDES PHASE II PROGRAM
The City owns and maintains a system of stormwater drains and pipes that are designed to carry stormwater (rain and snowmelt) from areas of potential flooding (ie: streets and parking lots) to the closest stream. This system, which also includes roadside ditches, is known as a municipal separate storm sewer system or MS4 for short. Unlike sanitary sewer systems, MS4s do not lead to a wastewater treatment plant. They carry stormwater directly, without treatment, to local waterways.
The U.S. Environmental Protection Agency and the Ohio Environmental Protection Agency enforce urban stormwater regulations. These regulations are associated with a program known as the National Pollutant Discharge Elimination System (NPDES). This program requires local governments to develop a plan to reduce stormwater pollution in order to protect and improve waterways.
The program is comprised of six control measures that will reduce pollutant discharge. These include the following:
- Public Education and Outreach: newsletters, websites and workshops relating to stormwater issues
- Public Participation and Involvement: programs and events that involve people in stormwater management (ie: the rain garden initiative and stream cleanup days)
- Illicit Discharge Detection and Elimination: ensures that only rainwater and snowmelt go down the drain
- Construction Site Runoff Control: review construction project's site plans to certify sediment, excessive runoff, and pollution will not enter streams or waterways
- Post-Construction Runoff Control: verify that runoff and pollution control structures are maintained
- Pollution Prevention and Good Housekeeping: measures taken by the City to protect waterways (ie: street sweeping and catch basin maintenance)
The City is required to submit a NPDES report for their MS4 system every year to the Ohio EPA in order to receive a permit to allow stormwater to enter streams and rivers. Click here to review the Gahanna's 2015 NPDES report.
ILLICIT DISCHARGE DETECTION AND ELIMINATION (IDDE) PLAN
The Illicit Discharge Detection and Elimination (IDDE) Plan is a component of the National Pollutant Discharge Elimination System (NPDES) program described above. This plan outlines how the City will find and eliminate pollutants that are entering the MS4 illegally to ensure that only rainwater and snowmelt go down the storm drain. Pollutants are categorized as anything other than clean rainwater or snowmelt. These ‘illicit discharges’ can enter through a storm drain on a street or parking lot, a pipe from a poorly functioning household sewage treatment system or a home or workplace drain connected to the MS4 instead of the sanitary sewer system.
The primary method that Gahanna uses to monitor pollutants entering its MS4 is dry-weather screening. Inspectors check outfalls, where storm sewer pipes empty to local waterways. If there has been no rain for a few days, and water is flowing from the pipes, where is it coming from? If it is clean, it may be from groundwater infiltration or a small stream that was enclosed in a pipe during development. Unfortunately, it is often from a poorly functioning septic system and is contributing nutrients, detergents and E. coli to a local stream. Other instances of illicit discharge might be washing machines incorrectly draining into basement sumps, car repair or other small business floor drains connected to storm sewer lines and homeowners dumping paint, automotive fluids, dead leaves, pet waste, etc down curbside storm drains.
Another important aspect of the City's IDDE plan is encouraging residents to report when they see or smell signs of pollutants in local streams or ditches. If you see or smell signs of pollutants please contact the Department of Public Service at 614-342-4005 between 8:00 am and 5:00 pm, Monday through Friday.
For more information and an opportunity to review the IDDE Plan, click here
. The City welcomes public comments on the plan. If you are interested in submitting comments, click here
STORMWATER MANAGEMENT PLAN
The City is required to submit a stormwater management plan to the Ohio EPA during the first term of the permit cycle. The report outlines the City's compliance status with permit regulations (such as NPDES), an evaluation of management procedures and analysis of progress goals. The Stormwater Management Plan can be found by clicking here